Significant efforts have been made to produce low density polyolefin materials to improve the use of natural resources and reduction of the carbon footprint in finished products. A typical approach to producing low density polyolefin materials is by foaming the polymer using physical or chemical blowing agents, which create gas cells though the bulk. Chemical blowing agents are compounds that undergo chemical reaction liberating gas that creates the cellular structure through the bulk of the polymer. Physical blowing agents are typically compressed gases that are dispersed in the polymer and expand creating the cells. Regardless, typical foaming processes induce low molecular orientation because the cell formation happens when the polymer is in the molten state. This prevents the polymer from strain hardening, which typically occurs at temperatures well above the melting temperature or glass transition temperature of the polymer, yielding products with low mechanical strength. Furthermore, typical foaming processes generate large cell sizes, such as greater than 100 μm. This reduces the melt strength, thus leading to breaks in high speed production processes with high deformation rates (e.g., fiber spinning, film formation, molding, etc.).
As such, a need currently exists for an improved technique in forming low density polyolefin materials.